1. FIELD OF THE INVENTION
This invention relates to an elevator mechanism for a tractor-scraper vehicle and, more particularly to an apparatus for limiting upward and downward movement of said elevator.
2. DESCRIPTION OF THE PRIOR ART
Tractor drawn scrapers have soil-cutting blades at the forward edge of the bowl, which bowl is provided with a continuous chain conveyor extending upwardly from the blade and forming the forward wall of the bowl. The elevator is driven to lift soil from the region of the blade, thereby reducing the resistance which the load offers to the movement of soil into the bowl. In some instances, the use of the elevator mechanism eliminates the need for a separate pusher tractor aiding the scraper in order to load the bowl.
It has been found that if the elevator is rigidly mounted on the scraper bowl, frequent stalling and damage occurs due to the elevator engaging relatively immovable objects, such as a large boulder or a rock which is too large to be elevated by the elevator into the bowl. To eliminate this problem, elevators have been mounted on a floating mount in such a way that the elevator can be pushed up to override large boulders or stones, or other obstructions, and can reposition itself when the obstruction is past.
One such floating mount is interconnected with a pivotal floor portion such that when the floor portion is pivoted to drop the load, the elevator is moved forward and upward to clear a large opening for dropping the load. Other types of linkage arrangements are also available whereby the elevator is moved forward and upward either to avoid obstructions in the loading operation, or in clearing the opening through which the load is being dumped. Guide and stop mechanisms have been provided which guide the direction of movement of the elevator forward and rearward and which prevent the elevator from being lowered beyond a predetermined level.
The prior devices made only limited provision for limiting the potential upward swing of the elevator relative to the blade. The result has been that the flights or bars on the elevator have been swung forward far enough to strike and gouge the spreader tube supporting the bowl on the tractor. Damage to the spreader tube or to the flights on the elevator can disable or reduce the effectiveness of the vehicle.